Interlimb differences in lower extremity bone mineral density following anterior cruciate ligament reconstruction.

Abstract

Prospective descriptive study. To determine the extent of bone mineral density (BMD) interlimb differences at several hip locations in the involved versus noninvolved lower extremity following anterior cruciate ligament (ACL) surgery. Disuse following ACL reconstruction can be extensive. This disuse not only affects the soft tissue, but may also affect the skeletal structure. The extent of this disuse specific to the proximal femur has not been previously determined. BMD was assessed in 15 subjects, 17 to 51 years old, who were between 6 and 32 months post-ACL reconstruction surgery. Bone mineral content (BMC) and BMD of the femoral neck, trochanteric region, intertrochanteric region, and entire hip were measured as a primary emphasis of this study. BMD and BMC of the entire lower extremities were also measured bilaterally. BMD was significantly less in the involved lower extremity compared to noninvolved lower extremity at several hip sites: 6.6% less (P<.001) for the trochanteric region, 4.0% less (P<.001) for the entire hip, and 3.4% less (P = .004) for the intertrochanteric region. No significant differences were noted comparing the entire lower extremities for either BMD (0.9%, P = .48) or BMC (3.7%, P= .09). BMD differences at the hip are significant in patient's postoperative ACL reconstruction, especially in the trochanteric region.